Batteries are devices in which a cathode electrochemically reacts with an anode to generate electricity. The batteries (for example, lithium ion secondary batteries) may be classified into a stacked type battery, a winding-type (jelly-roll-type) battery, or a stack and folding type battery according to structures of an electrode assembly.
In case of the stacked type battery, each of a cathode, a separator, and an anode is cut into a predetermined size, and then the cut cathode, separator, and anode are sequentially stacked to form an electrode assembly. Here, the separator is disposed between the cathode and the anode. In case of the winding-type battery, a cathode, a separator, a anode, and a separator, each of which has a sheet shape, are sequentially stacked and wound to form an electrode assembly. In case of the stack and folding type battery, a full-cell or a bi-cell is formed and then wound through a separator sheet to form an electrode assembly. Here, each of a cathode, a separator, and an anode is cut into a predetermined size and then sequentially stacked to form the full-cell or the bi-cell (the full-cell or the bi-cell includes at least one cathode, separator, and anode).
Recently, an electrolyte injected into a battery gradually increases in amount and viscosity according to increase in capacity of the battery. However, when an electrolyte increases in amount or viscosity, the electrolyte may be deteriorated in injectability, and thus it may take a long time to inject the electrolyte. This may act as a factor in reducing productivity (mass productivity) of the battery. In order to solve the above-described limitations, a method in which an electrolyte is directly heated to secure fluidity of the electrolyte is being considered. However, according to the above-described method, when the electrolyte is directly heated, the electrolyte may be volatilized to cause an offensive odor.